The invention concerns a method for the control and adjustment of a clutch in an automated stepped transmission for a motor vehicle with an interruption in traction during a shift procedure, wherein, an electronic control system with two control circuits determines the behavior of the said clutch. The invention further includes an apparatus for the execution of the method for the control and adjustment of a clutch in a transmission of a motor vehicle.
The term xe2x80x9cclutchxe2x80x9d, within the concept of the invention, encompasses the meaning, xe2x80x9cstarting clutchxe2x80x9d. This term includes clutches, which are placed between an internal combustion motor and an automatic transmission, clutches with capabilities to bypass torque converters, as well as clutches and brakes incorporated in automatic transmissions, which can be employed both for start-up and shifting purposes.
Especially, the invention concerns wet start-up clutches, which can be integrated into an automatic transmission. Mostly, such start-up clutches are to be found in combination units at the transmission input side, serving, for instance, as a starting element in an automatic transmission. In particular the said wet clutch is also of value as an assembly unit on the output side of continuously variable transmission (hereinafter CVT).
Normally, clutches and brakes in automatic transmission or in automated stepped transmission are electro-hydraulically activated, operating independent of intervention by the shifting elements. The said clutches and brakes then perform as gear position shifting means, assembly gear change clutches, start-up clutches or converter bypass clutches. To enable this service, usually an electronic transmission control apparatus processes, specifically for the individual vehicle, transmission and driving demands dependent upon the driving condition. These specifics can include axle gear ratios, transmission gear ratios, motor torque, motor rotation speed, throttle pedal position, and/or the like. The acquired data, as input, is transmitted to an electronic control apparatus and, by means of actuators and hydraulic valves, then converted into hydraulic control pressures designated for corresponding clutches. This latter data input would include, clutch related signals, such as, pressure control for pressure regulation or pressures during a gear change, and/or speed of rotation control during slip operation.
A procedure for the control of a start-up clutch, along with other matters, has been made known by DE 44 09 122 A1. The start-up control comprises, in this case, two phases. In a first phase, the input speed of rotation of the clutch is directed to a set-speed of rotation, wherein this set speed of rotation is determined by the driver""s demand for power and the current mode of driving activity. In the second phase, the difference between the input side and the output side speeds of rotation of the clutch is reduced to a set value of zero.
DE 39 37 976 discloses a procedure for the control of a clutch, which serves for clutch disengagement due to vibration disturbance. The slippage in the clutch, in this case, changes depending on speed of rotation equalization as determined at the transmission output.
EP 0 214 989 B2, again makes known the use of a clutch integrated in an automatic transmission as a start-up element.
DE 198 40 573, of the applicant, which up to now has not been published, describes a procedure for the control and regulation of a clutch in a stepless, automatic transmission for a motor vehicle, according to which, the control and regulation occurs during two driving conditions, by means of a first control circuit. The degree of this control corresponds to the set value of a difference in speed of rotation of the clutch. The first condition corresponds to a start-up process and the second condition corresponds to driving with a variable ratio arrangement.
From the likewise non-published DE 138 40 572 of the applicant, there is made known a process for the control and regulation of a clutch in an automated stepped transmission with traction interruption, that is to say, in an automated stepped transmission which can shift in accord with the load. With this method, during three conditions of driving (enumerated below), control is effected by means of a first regulating circuit. The degree of regulation, or control, corresponds to the set value of a difference in speeds of rotation of the clutch. The first condition of driving relates to a start-up process. The second condition of driving pertains to driving with a constant gear ratio. The third condition comes into play, when a load shifting, that is to say, a change of the ratio is initiated from a first into a second gear step of the automatic drive.
Given the above description of the state of the technology, the present invention has the purpose of making available a procedure for the control and regulation of a clutch in an automated stepped transmission for a motor vehicle along with an apparatus for the execution of said procedure for the control and regulation of a clutch, and to further develop the same with consideration given to the manifold usages of a single clutch, especially to achieve to an improved quality of regulation and control-dynamics, in connection with an automated stepped-transmission.
The object of the invention is to be found advantageously therein, in that for the control and regulation of the clutch during the first condition of driving, a first regulation circuit is employed. The degree of regulation corresponds to the actual value of the speed of rotation of the motor n_MOT_IST and corresponds to the input speed of rotation of the clutch. During the second condition of driving, a second regulatory circuit is used, the degree of regulation being equivalent to the actual value of the difference in rotational speeds of the clutch dnK_IST. Finally, during the third condition of driving, the clutch, which is subjected to controlled values of pressure which, in turn, are influenced by various factors. The three conditions of driving correspond, in the above to a first condition comprising a start-up procedure when under a threshold vehicle driving speed in traction operation, a second condition marked by driving the vehicle at a speed above the start-up procedure, i.e. above a threshold driving speed with a positive or negative torque in traction or compression mode and as well as driving under a vehicle threshold speed with a negative torque at output, and a third condition, wherein the start-up condition differentiates itself from the other driving conditions, in that the driving speed is less than a threshold value and the vehicle motor can stall under this said threshold value.
By means of the procedure in accord with the invention, advantageously, a better reaction of the transmission regulation is achieved in regard to load shifting, especially upon letting up on fuel feed in the third condition, since in this case, the control still performs an empty action upon the pressure at the clutch although no adjustment takes place.
Further, the difference of speeds of rotation over the clutch is not brought to a value of zero. The advantageous consequence of this is that a vibration disengagement between the motor and the transmission is achieved.
In a development of the invention, the proposal is brought forth, that the level of pressure, pAK of the clutch in the first and in the second condition can be calculated from the sum of an offset value pAK_OFF and a sum value pSUM. The sum value pSUM is determined principally from the balance of the controlled torque MK(ST) of the clutch, the regulated total torque MK(RE)xe2x80x2 of the clutch and the disengagement shift torque MLS_ENT.
The controlled torque MK(ST) is predominately determined from the dynamic torque of the clutch MDYN_K and the motor torque MMOT.
The regulated summation torque MK(RE)xe2x80x2 of the clutch is principally determined from the dynamic motor torque MDYN_MOT and a regulated torque MK(RE).
The regulated torque MK(RE) in the first condition of driving is to the greater part derived from the set/actual value comparison of one of the motor rotational speed n_MOT equivalent values and a loading demand of the driver DKI by means of a regulator.
The gear position dependent set difference of speeds of rotation dn_SW(i) for a start-up gear of the automated stepped transmission, in the second condition is arrived at by the characteristic engine map KF(i1) This engine map presents an association of the load demand of the driver DKI and the output speed of rotation nAB of the clutch.
During a traction interrupting shifting of the automated stepped transmission, there is carried out a switch shift from a gear position dependent characteristic field KF(i1) to a characteristic field KF(i2).
The regulated torque in the second driving condition MK(RE) is principally determined from the set/actual comparison of the speed of rotation difference dnK_SW, dnK_IST of the clutch and a load demand DKI of a driver in the regulator 6.
Advantageously, the regulator contains a limited integrator, whereby, the regulation deviation from the set/actual comparison of the speeds of rotation difference dnK_SW, dnK_IST of the clutch, the displacement speed of the load demand DKI and the ratio of actual value to the set value of the difference of speeds of rotation. dnK_IST/dnK_SW of the clutch are conducted to the said integrator as input values.
Again advantageously, in the transition from the first or third condition of driving into the second condition of driving the set value of the difference in speeds of rotation dnK_SW is conducted through a filter, especially a dynamic delay member, whereby, the actual value for the difference in speeds of rotation, this being dnK_IST, is input as a start-point for the delay timing.
Also, at this point, the transition is carried out between the gear step dependent characteristic field during the traction interrupted shifting.
The characteristic fields are, in this matter, so formulated, that in the case of a vehicle speed v, less than a threshold GW, an increased difference in speeds of rotation dn_SW(i) appears at the clutch. By this means, an effective stalling protection is achieved for the non-starting gear positions, these being the fourth or fifth gear of the automated stepped transmission.
Advantageously, also in the second condition of driving, at a vehicle speed v less than threshold value GW an increased difference in speeds of rotation dn_SW(i) in the clutch is created and serves as stalling protection. In connection with this, the increased difference in speeds of rotation is adjusted to be greater than the difference of the minimal speed of rotation of the internal combustion engine n_MOT_MIN and the output speed of rotation of the clutch nAB.
In the third driving condition, the level of pressure pAK at the clutch arises from a pressure value, which is dependent upon one or more of the following values: throttle flap position, motor torque, load shifting, or the like and wherein the pressure value has a controlled level.
Advantageously, also an apparatus for the execution of a procedure for the control and regulation of a clutch in an automated stepped transmission is made available. For this purpose, an electronic control apparatus with a first and second regulating circuit is provided, wherein the regulated size of the first regulation circuit is equivalent to the actual-value of the motor speed of rotation and the regulated value of the second regulation circuit is equivalent to the actual-value of a difference in speeds of rotation of the clutch.